Tiffany is 3 times as old as Emily and is also 10 years older than Emily. How old is Tiffany?
Answer: We can use the given information to write down two equations that describe the ages of Tiffany and Emily. Let Tiffany's current age be $t$ and Emily's current age be $e$ $t = 3e$ $t = e + 10$ Now we have two independent equations, and we can solve for our two unknowns. One way to solve for $t$ is to solve the second equation for $e$ and substitute that value into the first equation. Solving our second equation for $e$ , we get: $e = t - 10$ . Substituting this into our first equation, we get the equation: $t = 3$ $(t - 10)$ which combines the information about $t$ from both of our original equations. Simplifying the right side of this equation, we get: $t = 3t - 30$ Solving for $t$ , we get: $2 t = 30$ $t = 15$.